In recent years, nonionic surfactants in the form of an alkyleneoxide-low mole adduct of aliphatic alcohols, etc., which have a narrow molecular weight distribution have been noticed. If techniques for efficiently producing the low mole adducts are established, there is such an advantage that various anionic surfactants are derived from these low mole adducts as nonionic surfactants by further subjecting the nonionic surfactants to sulfonation reaction, phosphorization reaction, etc.
Hitherto, basic catalysts such as KOH have been extensively used for producing alkyleneoxide adducts. However, when using such basic catalysts, there tends to occur such a problem that the resulting nonionic surfactants have a broad molecular weight distribution. In 1970s, acid catalysts such as boron trifluoride and indium chloride have been noticed, whereas in 1980s to 1990s, homogeneous catalysts such as metal alcoholates, or heterogeneous catalysts such as phosphates of rare earth metals and mixed metal oxides have been noticed. However, it is known that even if it is attempted to produce the low mole adducts, for example, using a heterogeneous catalyst such as lanthanum phosphate catalyst, the resulting nonionic surfactants fail to have a narrow molecular weight distribution.
For example, Non-Patent Document 1 discloses that when using the heterogeneous catalysts, it is possible to obtain ethyleneoxide-7 mole adducts having a narrow molecular weight distribution, but the obtained ethyleneoxide-1 mole or 2 mole adducts are only those having a broad molecular weight distribution similarly to the case where the basic catalysts such as KOH are used. In addition, Non-Patent Document 2 discloses that even when using the heterogeneous catalysts such as mixed metal oxides composed of magnesium oxide and aluminum, it is difficult to obtain ethyleneoxide-1 mole adducts having a narrow molecular weight distribution.
On the other hand, Patent Documents 1 to 3 disclose nonionic surfactants composed of alkyleneoxide adducts of aliphatic alcohols. In addition, Patent Document 4 discloses a catalyst for alkoxylation of an aliphatic alcohol and an alkyleneoxide, and an alkyleneoxide adduct produced by using the catalyst. However, when these alkyleneoxide adducts are subjected to anionization process such as sulfation to derive anionic surfactants therefrom, there tends to occur such a problem that the resulting anionic surfactants suffer from undesirable coloration.    Non-Patent Document 1: “Nonionic Surfactants Organic Chemistry”, volume 72, p. 32    Non-Patent Document 2: “Oleo-Science”, Vol. 2, p. 97 (2002)    Patent Document 1: JP 53-119809A    Patent Document 2: JP 2001-11489A    Patent Document 3: JP 2001-40391A    Patent Document 4: JP 2005-305280A